The transition to a renewable energy future requires the development of sustainable chemicals and fuel refining technologies. Lignin, as the only renewable aromatic resource in nature, possesses ...tremendous potential for substituting environmentally detrimental and non-renewable fossil resources. Due to the complex structure and interaction of lignin components, the production of phenolic compounds from the thermochemical depolymerization of lignin were reviewed from the whole refining process. The findings highlighted that limitations and challenges with both individual lignin extraction methods and the extraction of phenolic compounds from bio-oil, such as low lignin purity, significant structural damage, poor conversion rate, etc. Importantly, research on lignin conversion methods has gone hand in hand, but none has yet achieved large-scale industrial application. Despite the significant role of catalysts in enhancing phenolic compound enrichment, current catalysts fall short of meeting the requirements for high catalytic activity and directional conversion. Meanwhile, the economic, technological, and environmental impact assessment of the industrial chain is also imperative. An optimized design of the whole chain from source extraction to intermediate conversion, targeted preparation and subsequent product application and emission helps to achieve efficient, targeted and industrialized application of lignin. Therefore, future endeavors should focus on integrating multiple technologies and methods to optimize the overall industrial chain design from source extraction to intermediate conversion, targeted preparation, subsequent product application, and emission. In addition, the focus should be on targeted conversion and extraction technologies for single phenolic platform compounds, with a view to achieving large-scale commercialization of the lignin-to-phenolic chemicals industry chain.
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•A whole chain of lignin-to-phenols was reviewed.•Extraction/structure of lignin and their influence on phenol production.•Lignin-to-phenol pathway routes has been elucidated in detail in this study.•Optimization of the whole chain of lignin to phenolic compounds was analyzed.•Future outlooks for lignin-derived chemicals and fuels are presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Natural phenolic compounds are rich in cereal and pulse seeds and their dietary functions tend to improve dramatically during germination. This article reviews recent research on the transformation ...of phenolic compounds during seed germination. In particular, it highlights the classification of crude phenolic compounds that can be divided into extractable and non-extractable phenolic compounds based on the biosynthesis process and extraction method. It also recommends grouping resorcinol lipids in the category of extractable phenolic compounds as non-polar solvent extractable phenolic compounds. Moreover, it discusses the variation of the different form of phenolic compounds and proposes a possible metabolic model of these phenolic compounds for seeds germination. This article is crucial for phenolic compounds research, cereal and pulse seeds germination, and food ingredients industry.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Combustion of organic solid wastes releases phenolic compounds which can act as precursors in the formation of environmentally persistent free radicals (EPFRs) in the post-flame, cooling zone of ...waste combustion. The study investigated the generation mechanism of EPFRs from phenolic compounds catalyzed by transition metals in air atmosphere under simulated combustion conditions. Representative combustion-derived phenolic compounds were used, and SiO2 particulates containing different mass ratio of Fe2O3 were synthesized as carriers. EPFRs formed had g-factors between 1.9998 and 2.0066, indicating phenoxyl-, cyclopentadienyl-, and semiquinone-type radicals, along with paramagnetic F-centers. The promotion effect of phenolic compounds on EPFR formation during heating decreased as catechol > hydroquinone > phenol > p-cresol. This trend is related to hydroxyl groups and activation energy. In particular, catechol chemically adsorbed on Fe2O3 at 600 K led to the formation of EPFRs with relatively high spin concentrations (up to 1.28 × 1017 spin/g). Higher Fe2O3 concentrations promoted the transformation of phenoxyl-type radicals into cyclopentadienyl-type and paramagnetic F-centers. However, as the Fe2O3 loading increased from 1.25% to 5%, the density of EPFRs decreased. The findings related to the influence of various precursors and Fe2O3 concentration on EPFR formation provide valuable insights for estimating EPFR generation and associated risk during combustion processes.
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•The underlying links between EPFRs and Phenolic Compounds were clarified.•The electron transfer between Fe2O3 and the precursor was determined by XPS.•A high concentration of Fe2O3 promotes cyclopentadienyl- and paramagnetic F-centers to form.•EPFRs concentration is related to the position of hydroxyl groups in the precursor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Phenolic substances in semi-coking wastewater were converted into phenolic resin by formaldehyde, therefore the resources were utilized. Volatile phenol, COD, ammonia nitrogen and oil in semi-coking ...wastewater before and after phenolic resin formation were detected to optimize the reaction time, temperature and raw material ratio, eventually the optimal reaction conditions for phenolic resin preparation were determined. Meanwhile, the physicochemical analysis of phenolic resin materials was carried out by XRD and SEM. The results showed that a volume ratio of 1:40 (formaldehyde vs. semi-coking wastewater), a reaction temperature of 90°C, and a reaction time of 4 hours were the optimum reaction conditions for semi-coking wastewater treated by formaldehyde.
This study provides a comprehensive chemical characterization of blueberry (Vaccinium corymbosum L.) pomace subjected to hydrolysis using carbohydrases (xylanase, cellulase and Extralyve®). Blueberry ...pomace obtained from the juice industry represents a rich source of insoluble dietary fiber, which holds potential for the liberation of oligosaccharides and phenolic compounds. Oligosaccharides were determined using HPLC-RID and change in phenolics were monitored by HPLC-DAD and HPLC-ESI-MS. Out of three enzymatic preparations, Extralyve®, which represents a commercial blend of xylanase, cellulase and polygalacturonase, demonstrated high hydrolytic activity towards the insoluble fiber present in blueberry pomace. This reduction led to an increased concentration of oligosaccharides, peaking after 2 h of hydrolysis (59.8 mg/g). Additionally, the levels of phenolic acids and non-anthocyanin flavonoids reached their maximum after 4 h of hydrolysis (1.22 mg/g), enhancing the antioxidant capacity of the hydrolyzed product (FRAP and ABTS assays). Finally, phenolic extracts from treated and untreated blueberry pomace were tested to evaluate cytotoxic potential in cell viability assays (MTT) using gastric carcinoma (NCI–N87) and two colorectal adenocarcinoma (Caco-2 and HT29-MTX) cells. Extracts obtained from Extralyve® treatment, rich in isorhamnetin, quercetin and kaempferol, resulted in interesting antiproliferative actions compared with the other treated and untreated samples.
•Carbohydrases broke down the insoluble dietary fiber (IDF) present in blueberry pomace (BP).•The combination of enzymes facilitated the release of phenolic acids and non-anthocyanin flavonoids.•The release of phenolics enhances the antioxidant and antiproliferative activities of blueberry pomace (BP) extracts.•The breakdown of insoluble dietary fiber (IDF) led to an increased generation of oligosaccharides.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
For many years, marine macroalgae are known to produce unique molecules with significant potential as natural products. These molecules include bioactive compounds and antioxidants, such as ...carotenoids, amino acids, proteins, lipids, vitamins, phenols and flavonoids. They have shown promising properties, including anti-coagulant, anti-proliferative, and antimicrobial effects. In this study we analyzed the antioxidant activity of 11 fresh methanolic extracts from marine macroalgae from the Canary Islands. Additionally, the effects of air-drying process in the antioxidant activity were evaluated. Total antioxidant activity methods included DPPH-free radical scavenging activity and ferrous iron chelating activity. Phytoconstituents evaluated were total carotenoids, proline, phenols, flavonoids and condensed tannins. The highest antioxidant activity was detected in the genus Lobophora, which was maintained after the drying process. However, differences were found between the species, with Lobophora dagamae presenting the highest activity. This high activity was consistent with the phenolic compounds analyzed. However, the highest ferrous iron chelating activity was obtained from Dictyota implexa and 3 Sargassum species, as well as in total carotenoids was Sargassum aff. polyceratium. This is the first record of the antioxidant activity to this species, revealing high potential for application in different industries, especially those that maintain this activity after drying process.
•Lobophora species presented the highest antioxidant activity and phenolic compounds•Lobophora species antioxidant activity was maintained after drying•The highest ferrous iron chelating activity was detected in Dictyota implexa•The highest carotenoids content was obtained in Sargassum aff. polyceratium•The highest proline content was recorded in Sargassum orotavicum
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Phenolics were extracted from MOLs using customised deep eutectic solvents (DES).•DES-based ultrasonic-assisted extraction (UAE) conditions were optimized by RSM.•DES-based UAE exhibited high ...efficiency for the extraction of the phenolic compounds.•DES-based UAE showed strong antioxidant activities.•Phenolic constituents in the MOLs extracts were analyzed.
In this study, an ultrasonic-assisted extraction (UAE) procedure with selected deep eutectic solvents (DES) as solvent was first designed to simultaneously optimize the total phenolic/flavonoid content (TPC/TFC) and antioxidant activities of Moringa oleifera L. leaves (MOLs) by using response surface methodology (RSM). The key factors for RSM were selected based on the design of the experimental results along with a three-factors-five-level, central composite design (CCD), including 20 experimental runs. The analysis of variance (ANOVA) results revealed that the water content in DES had a significant influence on all responses, while the ultrasonic time and the ratio of liquid to solid had no statistically significant effects on the total phenolic content. The optimal conditions of the combination of TPC/TFC and antioxidant activities were obtained as follows: 37% water content in DES, 144 W ultrasonic power, and 40 °C ultrasonic temperature. The measured parameters corresponded with the predicted results. Moreover, a comparative study confirmed that the optimized DES-based UAE yielded further higher TPC, TFC, and antioxidant activities than other extraction methods. The results of HPLC analysis in optimized conditions verified that the MOLs extracts with DES-based UAE included 14 phenolic compounds with high concentrations of vicenin-2 (17.6 mg/g) and orientin (23.6 mg/g). The present study supplied a green and high-efficient method for extracting high levels of anti-oxidative phenolic compounds from MOLs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Bound phenolic compounds have rarely been reported in vegetable oils and this may be due to little research about the extraction. Deep eutectic solvents (DESs), recently applied in the extraction of ...phenolic compounds as alternatives to organic solvents, were adopted in the extraction of free and bound phenolic compounds from tea seed oil in this work. First, the phenolic compounds were analyzed by ultra‐high‐performance liquid chromatography with quadrupole‐time‐of‐flight and triple‐quadrupole tandem mass spectrometry (UHPLC‐Q‐TOF‐MS/MS) for characterization and UHPLC‐QqQ‐MS/MS for quantification and 25 phenolic compounds were found to exist in both free and bound forms. Then, DESs were screened for extraction of free and bound phenolic compounds from tea seed oil as the pretreatment for analysis and the results showed that hydrogen bond donors (HBDs) and temperature significantly affected the extraction efficiency of DESs. Finally, free phenolic compounds (83.91 µg/g) and bound phenolic compounds (25.71 µg/g), extracted by the DES with glycerol as HBD at 50 °C, were 51.0% and 93.2% higher than those extracted by methanol/water (60%, v/v), respectively. This work not only advanced the basic data of phenolic compounds in tea seed oil but also explored an efficient extraction method for scientific analysis of free and bound phenolic compounds.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Schematic representation of the possible formation processes of hydrochars from lignocellulosic biomass via hydrothermal carbonization. Display omitted
► HTC allowed rapid conversion of biomass into ...a carbon-rich and lignite-like product. ► Carbonization involved in dehydration, decarboxylation, and demethanation processes. ► Solid residue and liquid product contained many value-added materials. ► Phenolic compounds and furan derivatives were analyzed by GC–MS.
Hydrothermal carbonization (HTC) is a novel thermochemical conversion process to convert lignocellulosic biomass into value-added products. HTC processes were studied using two different biomass feedstocks: corn stalk and Tamarix ramosissima. The treatment brought an increase of the higher heating values up to 29.2 and 28.4MJ/kg for corn stalk and T. ramosissima, respectively, corresponding to an increase of 66.8% and 58.3% as compared to those for the raw materials. The resulting lignite-like solid products contained mainly lignin with a high degree of aromatization and a large amount of oxygen-containing groups. Liquid products extracted with ethyl acetate were analyzed by gas chromatography–mass spectrometry. The identified degradation products were phenolic compounds and furan derivatives, which may be desirable feedstocks for biodiesel and chemical production. Based on these results, HTC is considered to be a potential treatment in a lignocellulosic biomass refinery.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
